1. Field of the Invention
This invention relates to dental impression trays, and more particularly to improved dental impression trays having a base and a trough for carrying dental impression composition into contact with teeth for making an impression, the tray having extended porous surfaces. In a particular aspect, the invention provides a dental impression tray capable of carrying a liquid such as water in contact with the dental impression composition so as to cool the impression composition. In other aspects, the invention provides a dental impression tray formed of sintered or fused individual metal or polymer bodies to have a desired degree of porosity, a roughened surface suitable for anchoring set impression composition for easy removal from the teeth, an occluded amount of liquid such as water useful for cooling a settable impression composition, the liquid suitably having a salt content for greater cooling capacity or medicaments for treating the mouth, a boss providing increased surface area in contact with the set impression composition, and/or a knife-carvable structure for ready adaptation to different size mouths or partial impression requirements. The porous surface and body as well in the invention dental impression tray is useful to absorb saliva in the mouth during the execution of dry field techniques.
2. Related Art
In dental practice, crowns, bridges and full or partial dentures are often fitted to patients to replace or repair the natural teeth. Each patient's mouth is unique in structural features so an effective crown or bridge to be comfortable must be closely fitted to the precise requirements of the individual. To ensure a close fit, an impression composition, comprising a natural or synthetic polymer that will set to a retained form, is applied to the areas to be replicated. The impression composition is necessarily impressionable and thus fluid. To carry the impression composition into the mouth, a dental impression tray is used. These trays comprise a base and a curvilinear trough generally sized and shaped to fit into the mouth and register with the patient's teeth. The impression material converts to a solid having in the negative the profile of the teeth and gums impressed into it. This impression is then used to form a stone model which is a positive of the teeth and gums. Then the bridge, crown or denture is fabricated using the stone model. Obviously, in all these steps errors in dimensions either from a faulty impression or a tearing of the set impression composition or a shrinkage or other distortion of the impression composition will adversely affect subsequent steps and result in a poor-fitting product.
The most exact dental impression composition is a hydrocolloid and it is the composition of choice when the highest quality impressions are desired. Usually, the hydrocolloid composition is applied to the teeth in the mouth in a heated, liquid form at about 110.degree. F. The hydrocolloid is set in situ by cooling to a set gel in about 5-10 minutes. And thereafter removed. Metal dental impression trays are provided with internal passages having an inlet and outlet. Cooling water is circulated through passages to cool and set the hydrocolloid by heat transfer from the hydrocolloid to the cooled metal tray. This procedure requires a ready water supply at the dental chair and is inconvenient in having to hook up the inlet and outlet hoses and maintain them in place while the tray is in the patient's mouth for the duration of the setting period.
Traditionally, dental impression trays have been metal appliances that offer the benefits of reusability, although sterilization and more recently universal precautions are required for this type of reusable tray. Metal trays are smooth surfaced, as are all dental trays of which the applicant aware, to more readily release the set impression composition, and for cleanliness, but have undercuts to retain the set composition with the tray when the tray is removed from the mouth. Plastic trays have been proposed, also smooth surfaced and having undercuts to retain the set impression composition so that these trays have essentially been plastic editions of the common metal trays.